Method of drawing metals



Patented July 18, 1939 PATENT. OFFICE 2,166,173 METHOD OF DRAWING METALS,

Harley A. Montgomery, Detroit, Mich.

No Drawing. Application June 23, 1937, Serial No. 149,946

5 Claims.

This invention relates to the cold working of metals, such as cold drawing operations and particularly to the cold drawing of tubing formed of ferrous metals such as alloy steels.

The present invention has for an object to provide a method facilitating the drawing of metals which is simple and inexpensive and which does not require special apparatus for its practice.

A further object is to provide a method by which surface defects due to excessive friction between the metal and dies are practically eliminated and by which a greater'and more uniform flow of metal may be obtained in a given drawing operation.

A further object is to provide a strongly adher- 16 ent coating for the metal which reduces friction between the metal and dies during the drawing operation and which is effective for a plurality of successive drawing operations.

In cold drawing steel tubing it has heretofore 20 been common practice to coat the interior and exterior "surfaces of the tubing after it has been annealed and pickled with a mixture of tallow, flour and Water, after, which the tubes were passed through a drying oven to dry the coating. The

tubes with the dried paste thereon were then drawn through a die and over a mandrel to reduce the diameter and wall thickness. Other water solutions or emulsions have been proposed, one of which is composed of water, waterglass and carbon black.

While fairly satisfactory results have been obtained with some steels by the use of coatings such as above described, manufacturing processes which include drawing, particularly in the manufactur'e of drawn steel tubing, have been quite expensive, due to the difficulty of effecting a substantial reduction in a single drawing operation and due to the cleaning, annealing and pickling, recoating and drying operations necessary be- 40 tween successive drawing operations.

5 mediate operations on the metal.

The drawing composition of the present invention is a composition which has an asphaltum base dissolved or thinned with a light hydrocarbon of relatively low infiammability, such as kerosene.

The asphaltum may be a vegetable distillation residue, a coal tar residue, or the residue of petroleum distillation. In any event the residue used as a base for the drawing composition of the present invention is a relatively dense product which orate upon application of a moderate heat. sufficient thinner is used to provide a liquid of the proper consistency for application in a thin coating to the surface of the metal. After the coated metal has been passed through a drying oven the liquid solvent is evaporated, leaving a thin dry and uniform coating of asphaltum, which is strongly adherent and which greatly reduces the friction between the metal and thedie elements during the drawing operation. The asphaltum coating has been found to be so adherent that a substantially continuous coatingremains on the metal after a drawing operation, which is effective for another drawing operation, so that a second drawing operation may be performed on the metal without any 15 further treatment of the metal.

It has been found advantageous to sulphurize the asphaltum prior to mixing with the thinner. The addition of sulphur improves the lubricating qualities of the asphaltum and lessens the dis- 20 placement of the lubricant during the drawing operation, thereby maintaining the uniformity of the coating on the metal during passage through the drawing die. The sulphurization of the asphaltum is accomplished by heating the asphal- 25 tum and adding about 10% of sulphur thereto. The asphaltum is heated to about 380 F. and the sulphur is then added a little at a time whilethe temperature of the asphaltum is allowed to rise to about 430 F. The temperature is then held at 30 about 430 F. 'forfrom 1 to 2 hours.

A petroleum asphalt of from 10 to 15 Baum specific gravity, sulphurized by the method above described, is a solid and the sulphurized petroleum asphalt may be dissolved in a sufiicient 5 amount of kerosene to provide a liquid of the desired consistency for coating the metal.

Furthermore, it is to be understood that the particular compounds disclosed, and the procedure set forth, are presented for purposes of explana- 40 tion and illustration and that various equivalents can be used and modifications of said procedure can be made without departing from my invention as defined in the appended claims.

What I claim is:

1. A method of cold drawing metal which comprises coating the metal with a solution of sulphurized asphaltum, evaporating the solvent and drawing the metal while thus coated.

2. A method of cold drawing metal tubing 50 which comprises coating the inner and outer surfaces of the tubing with a solution of asphaltum, evaporating the solvent and cold drawing the tubing while thus coated.

is dissolved in a suitable thinner which will evap- 3. Amethod ofcold drawing metal tubing which 55 sulphurized petroleum asphalt, drying the coating, and drawing the tubing while thus coated.

5. The method of cold drawing metal tubing which comprises forming upon the surface of the tubing a thin adherent coating of solid asphaltum 5 and cold drawing the tubing so coated.

' HARLEY A. MONTGOMERY; 

